The manufacturing of integrated circuits involves many process steps. After each of the manufacturing process steps, the wafers may need to be inspected to find defects, so that the yield of the respective process step may be determined. When the number of defects is great enough, and the yield is no longer acceptable, the manufacturing process needs to be halted, and steps need to be taken to improve the yield.
The determination of the yield typically includes two steps. In the first step, a wafer is inspected using an inspection tool, wherein dies in the wafer are compared so that potential defects may be found. The coordinates of the potential defects are recorded. In the second step, the wafer on which the potential defects are found is loaded on a review tool. The potential defects are reviewed manually to determine whether the potential defects are real defects or not.
The reviewing of the potential defects is typically time consuming. One of the reasons is that the inspection tool and the review tool have variations in determining the coordinates of the potential defects. The variations may range from several microns to about one hundred microns. As a result, in the review process, when no defect is found at a location of a potential defect, there may be two possible reasons. The first reason is that the potential defect is not an actual defect. This may be caused since the inspection tool is too sensitive and wrongfully identifies a non-defect as a defect. The second reason is that due to the variations in the inspection tool and/or the review tool, on the review tool, a wrong location is reviewed, while the actual defect is at a nearby location. To exclude the second possibility, the operator of the review tool has to search the nearby locations of the potential defect until either the defect is found, or until a nearby region that is large enough is searched, and no defect is found. Due to the effort required for the manual search of the possibility defects, the reviewing process is lengthy.